Moss graffiti may be one of the greatest things I have ever seen and I cant wait to try it somewhere.
Here's how you do it:
Put in blender, one can of cheap beer (or 1 1/2 cups buttermilk), a few handfuls of moss and a teaspoon of sugar.
Paint on wall in whatever words or shape you want.
Mist daily until it grows.
Just think of all the possibilities...